In some situations, it is desirable to know radio frequency (RF) signals expected to be received from the wireless transmitters (i.e. access points) in a given location in order to estimate locations of mobile devices. RF signals transmitted from, for example, Wi-Fi access points may be harvested (i.e. RF scan information is received and associated with absolute or relative position information of the mobile device) by mobile devices (i.e. collector devices) that are traveling through an environment using different modes of transportation (e.g. walking, driving, etc.), and are then used to estimate the locations of the mobile devices.